1. Field of the Invention
The invention relates to a control apparatus for a vehicle, and a method of controlling a vehicle. More specifically, the invention relates to a technology in which torque output from a power source is boosted during a torque phase when an automatic transmission upshifts.
2. Description of the Related Art
When an automatic transmission upshifts, a driving force decreases during a torque phase, and then the driving force increases and a shock occurs when the torque phase ends and an inertia phase starts. To suppress the shock when the automatic transmission shifts, the technology in which the torque is boosted during the torque phase, and the torque is decreased during the inertia phase is proposed.
Japanese Patent Application Publication No. 2004-314842 (JP-A-2004-314842) describes a shift control apparatus for an automatic transmission. When a gear shift is performed by engaging a friction element, the shift control apparatus executes an engaging-capacity control for the friction element and a torque decrease control that decreases torque output from a power source to reduce a shift shock during an inertia phase in which an effective gear ratio, which is the ratio of a rotational speed input to the automatic transmission to a rotational speed output from the automatic transmission, changes from a pre-shift gear ratio to a post-shift gear ratio. The shift control apparatus described in the above publication corrects the engaging capacity of the friction element based on the difference between a target power source torque that should be achieved by the torque decrease control, and the lower limit value of the power source torque. Also, the shift control apparatus executes a torque-boost control during a torque phase immediately before the inertia phase.
The shift control apparatus described in the above publication corrects the engaging capacity of the friction element through a feed-forward control to compensate for insufficiency in torque decrease because of the lower limit value of the power source torque. Because the engaging capacity of the friction element is corrected through the feed-forward control, it is possible to avoid a problem relating to slow response, which would arise if the engagement pressure is corrected through a feedback control. Thus, it is possible to reduce the difference in the output torque before and after the gear shift.
The engagement pressure (engaging capacity) is controlled based on the torque input to the automatic transmission during the inertia phase. Accordingly, if an accelerator pedal is operated during the inertia phase, the engagement pressure may be increased as the torque output from the power source, that is, the torque input to the automatic transmission increases. However, because the shift control apparatus described in the above publication executes the torque decrease control that decreases the torque output from the power source during the inertia phase, the torque input to the automatic transmission may decrease when an accelerator-pedal operation amount increases. If the engagement pressure is decreased based on the decreased torque input to the automatic transmission, the gear shift is slowly performed.